We previously identified a phosphatidic-acid-preferring phospholipase A1, which was present in high amounts in the mature testis and brain. Its special properties and distribution suggested that it could be playing a hitherto undescribed role in cell-signaling pathways. We therefore purified the enzyme, cloned and sequenced its cDNA, and examined both the distribution of the enzyme's messenger RNA and the distribution of the enzyme protein in primate tissues. We identified messenger RNA molecules of several different sizes and showed that they were distributed differently in different tissues and different regions of the brain. We also identified proteins of different sizes, which cross-reacted with antibodies to the phospholipase A1, and showed that they too were distributed differently in different tissues and different regions of the brain. The combined results of these and other experiments suggest that primate tissues may contain a family of proteins that are related to the enzyme. We are using techniques of molecular biology to investigate this possibility, and we hope to characterize the presumptive family of proteins in preparation for more detailed messenger RNA and protein mapping experiments in macaques.